The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A landing gear bay is a housing intended to receive a landing gear of an aircraft.
In most aircraft for transporting merchandise or people, the gear bay is located in the fuselage of the aircraft and is usually closed by an opening and closing system including several hatches.
There are several opening and closing systems.
Typically, an opening and closing system, or hatch system, includes at least two main hatches, for example the front gear hatches, which open for allowing the deployment of the gear and close when the gear is out so as to limit aerodynamic disruptions.
This system also includes at least two secondary hatches, for example the rear gear hatches, which open for allowing the deployment of the gear and remain open as long as the gear is out.
The system may also include a fifth hatch, called central hatch or main leg fairing, which, like the secondary hatches, remains open as long as the gear is out. The main leg fairing is usually secured on the gear, more particularly on a gear leg.
A landing gear hatch, more simply called gear hatch, usually comprises a panel secured on hinge arms, generally goosenecks hinged on the structure of the aircraft, around a pivoting axis shifted inwardly in the gear bay with respect to the panel.
Goosenecks are generally distributed over the length of the hatch and secured, on the one hand, on the hatch and, on the other hand, on the structure of the aircraft.
Depending on the case, at least one gooseneck is connected, by means of a connecting rod, to the structure of the aircraft. Alternatively, the connecting rods may be secured to the hatches by other types of platings.
This connecting rod allows performing a rotational movement of the hatch with respect to the fairing of the aircraft. According to the forms, there may also exist a system of intermediate bell-cranks aiming to limit the load along the longitudinal direction of the aircraft and allowing reducing the size of the platings along this direction.
Thus, during the deployment of the landing gear, the pivoting of the hatch towards the outside of the fuselage is obtained by means of the connecting rod and gooseneck hinges.
While the front hatches are generally displaced by means of at least one actuator (they open before the deployment of the gear), each secondary hatch is connected to the landing gear, for example by means of a connecting rod secured, on the one hand, on the landing gear (for example on the gear leg or on a hinge triangle of the gear) and, on the other hand, on the hatch.
This connecting rod allows maneuvering the hatch directly according to the movements of the landing gear. Thus, during the retracting of the landing gear, the actual fact that the landing gear ascends into the gear bay provides the closing of the hatch. The same can be said for the deployment of the gear and the opening of the hatches. Alternatively, it can also be considered to use a hinge triangle on the gear leg instead of the connecting rod(s).
More particularly, while the gear is deploying, the latter turns about an axis (forming the hinge triangle), causing a movement of the connecting rod which pushes the hatch to its open position.
Such a configuration hence allows controlling the deployment of the landing gear and the opening of the hatch at the same time.
In order to preserve the aerodynamics of the fuselage of the aircraft, the arrangement of the pivoting axis of the landing gear is achieved inside the gear bay. As mentioned before, the front hatches close up after having left the landing gear pass in order to reduce aerodynamic disruptions. Due to the passage of the gear leg, it is difficult and sometimes not possible to close the rear hatches again, thereby causing significant aerodynamic disruptions along the fuselage of the aircraft.
For these aerodynamic reasons, the secondary hatches have a reduced surface and opening which just allow the deployment of the landing gear. The front hatches should allow the passage of the landing gear wheels and are by comparison relatively wider.
A four hatch system generally does not comprise a main leg fairing.
In the case of a four hatch system, there are generally two rear hatches, or secondary hatches, and two front hatches, or main hatches, placed side by side.
The rear hatches may open in several ways.
As described above, the hatches may generally open laterally by pivoting.
Various hatch opening systems are described in Patent Documents: FR 2 911 321, FR 2 922 519, FR 2 886 620, US 2009/0159743 and U.S. Pat. No. 7,458,542.
French Patent FR 2 886 620 describes a system in which the hatches open laterally on either side of the fuselage, by pivoting. The rear hatches are fastened to the landing gear, by means of a rocker arm. This system is more particularly intended for large planes, of the A380 type, having a vast gear bay allowing housing therein the hinge system and the additional connecting rod. Such a system is difficult to implement on gear bays of smaller aircrafts.
U.S. Patent Publication US 2009/0159743 also describes a hatch system (five hatch system) with a lateral opening and by pivoting, including for the main leg fairing.
U.S. Pat. No. 7,458,542 describes an opening and closing system in which the front hatches have a double rotational movement, of tilt-and-turn type, such as to adopt an intermediate position in which they serve as aerodynamic cowling upstream of the deployed gear.
French Patent FR 2 922 519 describes a hatch system for gear bay animated by a lateral circular translational movement by means of deformable parallelogram type hinge. A gooseneck provides the detachment of the hatch and the lateral displacement thereof, the deformable parallelogram maintaining the orientation thereof substantially horizontal.
It is worth noting that the driving of these hatches is not carried out by means of the gear leg but by means of independent control means of cylinder type actuating a dedicated gooseneck type hinge.
At the start of its opening movement as well as at the end of closing, the lever arm exerted by this cylinder is extremely reduced, thus making the cylinder able to develop an even more important power and to be dimensioned accordingly. The hinges must also be dimensioned accordingly, thus translating by an unwanted increase of their size, bulk and mass.
It is also worth noting that the deformable parallelogram is constructed from a transversal hinge axis of the landing gear leg, thereby inducing positioning constraints of the hatch hinge system.
As for French Patent FR 2 911 321, it aims some aircrafts, particularly transport aircrafts intended for transporting cargo, in which there are certain constraints as regards the positioning of the floor.
French Patent FR 2 911 321 mentioned above describes a system for opening and closing a landing gear bay including at least one secondary hatch opening not laterally but longitudinally, so as to be in the direction of flow of the fluids. The hatch is further animated by a circular translation movement maintaining it substantially parallel to the fairing of the aircraft and to the flow of the fluid.
The hinge of the hatch is carried out by means of a gooseneck hinge rotatably secured, on the one hand, to the fairing, a stationary part of the aircraft, and on the other hand, to the hatch.
The driving of the hatch is associated to the landing gear leg and is carried out by means of a drive rod stiffly mounted on said gear leg but pivotally mounted on the hatch.
The stationary characteristic of the drive rod allows providing the translational guiding of the hatch and the maintaining thereof in a plane which is substantially parallel to the lines of the aircraft.
However, we have discovered that such a drive architecture is relatively stiff and not adaptable.